Fault tolerant MOSFET driver

Abstract

A MOSFET switched, redundant power supply has a back-to-back MOSFET switch connecting respectively each power supply to a single load. Each power supply has a positive and negative gate voltage source. In a specific N-channel MOSFET embodiment, the positive (i.e. on) bias is coupled to each switch via a radiation hardened, redundant analogue switch capable of being driven by, for example, a TTL or CMOS microprocessor signal. The negative (i.e. off) bias is coupled to each via a redundant diode pair. In addition, the gates of the back-to-back MOSFET switch for one power source are also connected to the negative bias of the other power source. In this way the MOSFET switch for a failed power supply will be maintained in an off state by the negative bias provided by the redundant supply.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is as follows: 
     
       1. A fault tolerant MOSFET driver circuit for turning on and off MOSFET switches, which couple two or more redundant power sources to a load, comprising in combination: a first power source including a positive bias means, a negative bias means, a load power means, and a first control signal source;   a second power source including a positive bias means, a negative bias means, a load power means, and a second control signal source;   a first MOSFET switch means having a source, a drain and a gate for connecting said load power means of said first power source to said load;   a second MOSFET switch means having a source, a drain and a gate for connecting said second power source to said load;   means responsive to said first control signal source for connecting said positive bias means of said first power source to said gate of said first MOSFET switch;   means for coupling said gate of said first MOSFET switch to said negative bias means of said first power source;   means for coupling said gate of said first MOSFET switch to said negative bias means of said second power source;   means responsive to said second control signal source for connecting said positive bias means of said second power source to said gate of said second MOSFET switch;   means for coupling said gate of said second MOSFET switch to said negative bias means of said second power source; and   means for coupling said gate of said second MOSFET switch to said negative bias means of said first power source.   
     
     
       2. A fault tolerant MOSFET driver circuit for turning on and off MOSFET switches, which couple two or more redundant power sources to a load as in claim 1 wherein said MOSFET switches are not radiation hardened. 
     
     
       3. A fault tolerant MOSFET driver circuit for turning on and off MOSFET switches, which couple two or more redundant power sources to a load as in claim 1 wherein said MOSFET switches are N-channel of, enhancement mode devices. 
     
     
       4. A fault tolerant MOSFET driver circuit for turning on and off MOSFET switches, which couple two or more redundant power sources to a load as in claim 1 wherein said means responsive to said control signal source is a radiation hardened switch. 
     
     
       5. A fault tolerant MOSFET driver circuit for turning on and off MOSFET switches, which couple two or more redundant power sources to a load as in claim 1 wherein said means for coupling said gate of said first MOSFET switch to said negative bias means of said first power source includes a redundant diode pair. 
     
     
       6. A fault tolerant MOSFET driver circuit for turning on and off MOSFET switches, which couple two or more redundant power sources to a load as in claim 1 wherein said means for coupling said gate of said first MOSFET switch to said negative bias means of said second power source includes a redundant diode pair. 
     
     
       7. A fault tolerant MOSFET driver circuit for turning on and off MOSFET switches, which couple two or more redundant power sources to a load as in claim 6 wherein said means for coupling said gate of said first MOSFET switch to said negative bias means of said second power source includes a redundant diode pair. 
     
     
       8. A fault tolerant MOSFET driver circuit for turning on and off MOSFET switches, which couple two or more redundant power sources to a load, comprising in combination: a first power source including a positive bias means, a negative bias means, a load power means, and a first control signal source;   a second power source including a positive bias means, a negative bias means, a load power means, and a second control signal source;   a first MOSFET switch means having a source, a drain and a gate for connecting said load power means of said first power source to said load;   a second MOSFET switch means having a source, a drain and a gate for connecting said second power source to said load;   means responsive to said first control signal source for connecting said negative bias means of said first power source to said gate of said first MOSFET switch;   means for coupling said gate of said first MOSFET switch to said positive bias means of said first power source;   means for coupling said gate of said first MOSFET switch to said positive bias means of said second power source;   means responsive to said second control signal source for connecting said negative bias means of said second power source to said gate of said second MOSFET switch;   means for coupling said gate of said second MOSFET switch to said positive bias means of said second power source; and   means for coupling said gate of said second MOSFET switch to said positive bias means of said first power source.   
     
     
       9. A fault tolerant MOSFET driver circuit for turning on and off MOSFET switches, which couple two or more redundant power sources to a load as in claim 8 wherein said MOSFET switches are not radiation hardened. 
     
     
       10. A fault tolerant MOSFET driver circuit for turning on and off MOSFET switches, which couple two or more redundant power sources to a load as in claim 8 wherein said MOSFET switches are N-channel of, enhancement mode devices. 
     
     
       11. A fault tolerant MOSFET driver circuit for turning on and off MOSFET switches, which couple two or more redundant power sources to a load as in claim 8 wherein said means responsive to said control signal source is a radiation hardened switch. 
     
     
       12. A fault tolerant MOSFET driver circuit for turning on and off MOSFET switches, which couple two or more redundant power sources to a load as in claim 8 wherein said means for coupling said gate of said first MOSFET switch to said negative bias means of said first power source includes a redundant diode pair. 
     
     
       13. A fault tolerant MOSFET driver circuit for turning on and off MOSFET switches, which couple two or more redundant power sources to a load as in claim 8 wherein said means for coupling said gate of said first MOSFET switch to said negative bias means of said second power source includes a redundant diode pair. 
     
     
       14. A fault tolerant MOSFET driver circuit for turning on and off MOSFET switches, which couple two or more redundant power sources to a load as in claim 13 wherein said means for coupling said gate of said first MOSFET switch to said negative bias means of said second power source includes a redundant diode pair.